Gaining or losing weight in between pregnancies can have major health implications for an unborn baby

Gaining or losing weight in between pregnancies can have major health implications for an unborn baby, warn two senior obstetricians in the British Medical Journal.

While weight and obesity have long concerned women in relation to body image and lifestyle issues, few are aware of the possible risks that fluctuating weight could have on their unborn child, write Dr Jennifer Walsh and Professor Deirdre Murphy.

They point to two studies. The first, from Sweden, which found that weight gain between pregnancies was strongly associated with major complications for the woman and baby in the months preceding, during and just after childbirth. This was independent of whether a woman was, by definition, overweight.

The researchers studied 207,534 women from the beginning of their first pregnancy to the beginning of their second. They found increased rates of pre-eclampsia, diabetes in the expectant mother, pregnancy induced high blood pressure and high birth weight if a woman's body mass index (BMI) increased by just one to two units. A rise of more than three BMI units significantly increased the rate of stillbirths.

The key message, say the authors, is that women of normal weight should avoid gaining weight between pregnancies, while overweight and obese women are likely to benefit from weight loss before becoming pregnant.

The second study looked at whether a change in the mother's nutritional balance increased the risk of a premature birth. They found that women whose BMI fell by five or more units between pregnancies had a higher risk of giving birth prematurely than women whose weight remained stable or increased. The risk was significantly higher for women who had already had a premature birth (80% versus 28%).

"Although apparently conflicting, these studies show how important it is to attain and maintain a normal healthy weight before, during, and after pregnancy," say the authors.

Most women want to achieve the best start in life for their babies, they add. This could be a powerful motivational factor in helping them change the way they eat.